Prior Art related to this disclosure includes U.S. Pat. Nos. 4,170,727 (Wilkins); 4,324,971 (Frappier); and 4,017,707 (Brown et al). Generally, Wilkins discloses a thermal torch height acquisition circuit having an DC arc length control to vary the arc motor speed. The measured variable is the voltage between the torch and the work piece, which increases as the torch is moved closer to the work piece. This voltage is compared with a selected reference voltage from which torch height control is determined. The motor is operated to raise or lower the torch as a result of the comparison. Brown sets out a plasma arc torch control system. The voltage between the work piece and torch is sensed and a signal representative of the difference between the sensed voltage and an adjustable reference is then created. A motor cooperative with a power supply is used to move the torch relative to the work piece. Frappier is a torch height acquisition system having a current sensitive relay in the arc supply circuit. The relay has normally closed contacts connected in the motor drive power supply circuit. The relay contacts are opened after main arc ignition has been sensed.